1. Background
The present disclosure relates to electrosurgical forceps for assuring uniform sealing of tissue when performing electrosurgical procedures. More particularly, the present disclosure relates to open, laparoscopic, or endoscopic bipolar forceps that improve the uniformity of current distribution through tissue and create a seal having a substantially uniform tissue thickness, by improving parallelism of the electrode faces of the bipolar forceps.
2. Technical Field
Forceps utilize mechanical action to constrict, grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis by heating the tissue and blood vessels. By controlling the intensity, frequency and duration of the electrosurgical energy applied through jaw members to the tissue, the surgeon can coagulate, cauterize and/or seal tissue.
In order to effect a proper seal with larger vessels or thick tissue, two predominant mechanical parameters must be accurately controlled—the pressure applied to the tissue and the gap distance between the electrodes. As can be appreciated, both of these parameters are affected by thickness of vessels or tissue. More particularly, accurate application of pressure is important for several reasons: to oppose the walls of the vessels; to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness which is an indication of a good seal. It has been determined that a fused vessel wall is optimum between 0.001 and 0.006 inches. Below this range, the seal may shred or tear and above this range the lumens may not be properly or effectively sealed.
With respect to smaller vessels, the pressure applied to the tissue tends to become less relevant whereas the gap distance between the electrically conductive tissue sealing surfaces becomes more significant for effective sealing. In other words, the chances of two electrically conductive sealing surfaces touching during activation increases as the vessels become smaller.
Electrosurgical methods may be able to seal larger vessels using an appropriate electrosurgical power curve, coupled with an instrument capable of applying a large closure force to the vessel walls. It is thought that the process of coagulating small vessels is fundamentally different than electrosurgical tissue vessel sealing. For the purposes herein “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried and vessel sealing is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass. Thus, coagulation of small vessels is sufficient to permanently close them. Larger vessels need to be sealed to assure permanent closure.
Numerous bipolar electrosurgical forceps have been proposed in the past for various surgical procedures. However, some of these designs may not provide uniformly reproducible pressure to the blood vessel and may result in an ineffective or non-uniform seal. Complicating matters further is the fact that a non-uniform pressure applied to a blood vessel creates varying tissue thickness along the length of the forceps. The result is varying pressure being applied, varying tissue thickness, and varying amount of electrosurgical energy passing through the tissue. All of these conditions reduce the effectiveness of the seal